Diffraction chromoscope.



No. 898,369. PATENTBD SEPT. a, 1908. F. E. IVES.

DIFFRAGTION CHROMOSGOPE.

APPLICATION FILED MAR. 21, 1906.

2 SHEETS-SHEET 1.

PATENTBD SEPT. 8, 1908.

P. E. IVES.

DIPPRACTION CHROMOSCOPE.

APPLICATION FILED MAR. 21, 1906.

2 SHEETS-SHEET 2.

UNITED STATES PATENT OFFICE.

FREDERIO EQIV ES, OF WEEI'IAWKEN, NEW JERSEY DIFFRACTION CHROMOSCDPE.

To all whom it may concern:

Be it known that I, FREDERIC E. IVES, a citizen of the United States,residing in oodcliffe-on-Iludson, IVeeliawken, New Jersey, haveinvented. an Improved Diffraction Chromoscope, of which the following isa specification.

Diffraction color photographs consist of three superposed or mixed.images printed in fine diffraction lines in clear gelatin or albumen, torepresent the three primary colors and their combinations. The spacingof the diffraction lines is different for the different color elements,say 2,000 lines to the inch for the red, 2,600 for the green, and 2,900for the blue. Viewed by perfectly diffused trans mitted light thesephotographs are quite invisible, but can be made visible with anapproximation to the natural colors by viewing them in special devicewith a point or line of light, a portion of which is dispersed andlaterally displaced by the diffracting lines of the photograph, andfocused upon the eye by means of a suitable lens. The source of light isusually a gas or lamp flame turned edgewise to the axis of the lens andat a distance of several feet from it. One objection to this device isthat the color of a gas flame is not suitable for obtaining the bestresults and another is that some considerable skill is required to makethe necessary adjustments, and they are lost again by a very slightdisturbance of the instrument. Some of the diffraction photographs alsorequire to be viewed by first order spectra and others by second. orderspectra in order to give the best results, and the necessary changes ofadjustment are troublesome and likely to be very imperfectly performedby any but skilled exports.

The object of my invention is to so exhibit a diffraction colorphotograph that satisfactory illumination can be obtained either byartificial light or by diffused daylight, and iiicidentally to permitfixed adjustment and convenient disposition of the variousinstruincntalities necessary to such exhibition so that no skill isrequired in order to obtain successful results.

In the accompanying drawings, Figure 1 is a diagrammatic re'iresentation of means heretofore employed for exhibiting a diffractioncolor photograph; Fig. 2, is a longitudinal sectional view of a devicefor exhibiting such photographs in accordance with my invention; Fig. 3,is a plan. view of the same;

Specification of Letters Patent.

Application filed March 21, 1906.

Patented Sept. 8, 1908.

Serial No. 307,215.

Fig. 4, is a longitudinal sectional view of ana focusing lens, ."c .aposition where the lens c appears filled with white light, and w aPOSltion where the graduated spectra of one order are suitablysuperposed and focused upon the eye, red spectrum rays from one gratingphotograph image, green from. another and blue from the third, so thatthere appears to be a color photograph at b. At i/ spectra of the secondorder may be similarly utilized. On the other side of the axis aresimilar spectra, either of which may be utilized. If the axis of theinstrument is suitably displaced with respect to the position of a thewhite light may be made to focus at w and the superposed spectra at a:or the white at 3 and the superposed second order spectra at A larger orcloser source of light may be used by placing it behind a slit in anopaque screen, such as shown by dotted lines at a, and inserting anotherlens such for instance, shown by dotted lines at c to parallelize therays, and this method of procedure would even admit of the use ofdiffused daylight, but for the fact that where spectra of only one orderare utilized, as in the device described, diffused daylight does notgive sufliciently strong illumination to be satisfactory.

I overcome the objections to the present procedure, first, by usingmultiple slits or sources of light so disposed as to utilize two or moreof the spectra from each diffraction image, thus doubling, or even,under certain conditions, quadrupling the illumination, secondly, byattaching the slitted diaphragm to the viewing device so that the adjustments are fixed, and thirdly, by making a turn in the axis of theinstrument, with a base line so disposed as to inake the angles ofillumination and vision more convenient and satisfactory.

In Fig. 2, of the drawings, A and B represent, respectively, the baseand easing of the instrument, hinged together at O. D is a slit near theeyepoint, E and F are lenses, G is a mirror and the line II, is thenormal optical axis. J are grooves for receiving the diffractionphotograph slides and K, I, K K are slitsin an opaque screen L, attachedto one end of the case. M, M are lines showing the form of a cone ofnormal axial venient use of a window or other source of rays on bothsides of the lenses F and E, light, as well as for convenient viewing ofthe which are separated not only to permit of the insertion of thediffraction photograph, but in order to permit of changing its positionto suit eyes having either long, normal or short sight, and thisseparation may possibly be reduced to some advantage in other respects.In the absence of a diffraction photograph between the lenses E and F,light entering the slot D would normally be focused upon the inside ofthe opaque diaphragm IJ at its center, and light passing in the otherdirection through the slits K, K, K, K" would be thrown above or belowthe slit D, and so lost to vision. When, however, a diffractionphotograph is inserted between the lenses E, F, the diffraction lines inthe photograph, dispersing and deflecting light from D, would throwsuperposed spectra on all of the slits, K, K, 1L li and, conversely, allof the first and second order spectra obtained from light coming throughthe slits K, K 1Q, 1Q, would be superposed at D. The diffraction)hotograph would therefore be seen by the light of four sets of spectranamely, first and second order spectra on each side, and theillumination would be greatly increased over that which would beobtained by utilizing only one set of spectra. If the slits R, l!belonging to the second order spectra be made twice as wide as thosebelonging to the first order spectra, which is permissible, be cause thedispersion is twice as great, the illumination may possibly bequadrupled compared with that obtained with one set of first orderspectra. This arrangement possesses other advantages which may be lessobvious, but are of considerable practical importance. For example, someof the diffraction photographs throw more light into the second orderspectra than into the first, and vice versa, and sometimes thediffraction lines belonging to one of the superposed or mixed images actdifferently in this respect from those belonging to the others, andsometimes one side or portion of the diffraction photograph actsdifferently in this respect from the other side or portion. The mixingof the several spectra corrects errors thus introduced into singlespectrum images, and makes the reproduction not only more brilliant, butmore correct and harmonious.

In addition to the advantages already enumerated, the use of slitshorizontally disposed and of appropriate length, or appropriatelyspaced, together with diffraction photographs having the diffractionlines horizontally disposed, permits the images to be viewed with botheyes at once, and I believe that binocular vision with the eyes onopposite sides of the normal axis of a diffraction photograph viewingdevice is also a new and valuable improvement. The bend in the axis ofthe light rays provides for the conimages.

My improved viewing instrument, while calculated to operate mostsuccessfully in diffused daylight, may be very satisfactorily used withartificial light by placing it near the source of light, with a groundglass over the diaphragm L, and the color of the light may be modifiedand improved by adding also a pale cobalt blue glass Z or othermodifying screen.

The instrument shown in Fig. 4-, has for its object greater simplicityand compactness of construction, and increased illumination of thediffraction photograph images. In this instrument is employed a lens X,preferably a convex meniscus, with the concave curve on a radiuscorresponding to the focal dis tance. This lens serves to focus both theeye slit D and the spectrum slits K, K K and li A. plane mirror P isplaced behind the diffraction photograph f), and a divided or two-partplane mirror, inclined at an angle of -l5, is employed behind thespectrum slits, as shown at G, the rays of light passing to the eye slitbetween the two parts or sections of said mirror. By this means thesecond lens and the extension of the case are eliminated, and otherimportant advantages are obtained, thus, in the instrument shown in Fig.2, only a comparatively small portion of the light incident on adiffraction photograph is diffracted, whereas in the instrument shown inFig. 4. the li ht )asses twice through the photograph, and the totalamount of light diffracted is increased by considerably more than fiftyper cent. Yiewed axially the images are so perfectly superposed as toappear as a single sharp image, even when the diffraction photograph andmirror are considerably separated, because the light rays are parallelto each other to and from the lens N on the side of the mirror P. Vi'henthe diffraction photograph and the mirror are separated, however, andthe compound image is viewed other than axially, as with binocularvision from two sides of the axis, said image appears doubled inoutline, hence, in order to obtain binocular vision with practicalcoincidence of images, the glass of the mirror P is made quite thin,usually about one millimeter thick, and the diffraction photograph,without cover glass,

is laid face downward upon it, with only paper or very thin metalseparators, under which conditions doubling of outline, seen withbinocular vision, is negligible, and when the diffraction photographsare made to mix the primary colors by juxtaposed colored lines it isfound that the linear structure is much. less noticeable than when onlya single image is formed, as in the instrument shown in Fig. 1, and thisis also an important gain. In an instrument of this type I may use aill) Cir

in Figs. 5

diaphragm L with but a single spectrum slit, such for instance as shownat K in Fig. 5, the rays of light from this slit being reflected bymirrors G disposed on opposite sides of the eye slit, and preferablysusceptible of angular adjustment, as for instance by hinging them at i,and pressing the same in one direction by means of springs m and in theother direction by means of adjusting screws a, this arrangementproviding for the utilization of right and left spectra with a singleslit, and, if desired, a plurality of adjustable mirrors G may beemployed on each side of the eye slit, as shown in Fig. 6, for theutilization of spectra of different orders. When the source of light isconcentrated, as for instance when it is derived from a gas burner, anelectric are light, or the like, it may be advisable to refract certainof the rays so as to properly direct them to the mirrors on oppositesides of the eye slit, and for this purpose a suitable refracting devicein front of the diaphragm L may be used, the device preferred for thispurpose being a prism, such, for instance, as shown at S, in Fig. 7.

In an instrument of the character shown and 6, the mirrors G may beregarded as duplicators of the single slit K, since the reflected raysfrom the separate inclined mirrors are parallel to each other, exactlyas the reflected rays from separate slits in Fig. 4, and thisarrangement is therefore an optical equivalent to that shown in Fig. 4,for the production of superposed spectra at the eye slit D.

I claim 1. A diffraction color photograph viewing device having aplurality of separated sources of light disposed to superpose at theview point two or more of the spectra belonging to each diffractionruling.

2. A diffraction color photograph viewing device having a plurality ofseparated sources of light, disposed to superpose at the view pointright and left spectra belonging to each diffraction ruling.

3. A diffraction color photograph viewing device having a plurality ofseparated sources of light disposed to superpose at the view pointspectra of two or more orders belonging to each diffraction ruling.

4. A diffraction color photograph viewing device having a diaphragm witha plurality of slits disposed to superpose at the view point two or moreof the spectra belonging to each diffraction ruling.

5. A diffraction color photograph viewing device having a diaphragm witha plurality of slits disposed to superpose at the view point right andleft side spectra belonging to each diffraction ruling.

6. A diffraction color-photograph viewing device having a diaphragm witha plurality of slits disposed to superpose at the view point spectra oftwo or more orders belonging to each diffraction ruling.

7. A diffraction color-photograph viewing devicehaving slits for firstand second order spectra, those for the second order spectra being ofthe greater area.

8. A diffraction color-photograph viewing device having horizontal slitsof such length or spacing as to permit of binocular vision of a singletri-color image. I

9. A diffraction color-photograph viewing device having a viewing end, alight receiving opening, and a mirror disposed therebetween to bend theoptical axis.

10. A diffraction color-photograph viewing-device having a viewing end,means for receiving a photograph, and a mirror serving as 'a backing forsaid photograph, said mirror being disposed in a plane parallel to saidphotograph so that light passes twice through a the photograph beforereaching the eye. I 11. A diffraction color-photograph viewing devicehaving a mirror serving as a back ing for the photograph and havinganother mirror disposed to bend the optical axis.

12. A diffraction color-photograph viewing device having an eye slit,and mirrors disposed to bend the optical axis, and separated to permitpassage between them of the rays of light to the eye slit.

13. A diffraction color-photograph viewing device having an eye slit, amirror serving as a backing for the photograph, and mirrors disposed tobend the optical axis and separated to permit passage between them ofthe rays of light to the eye slit.

14. A diffraction color-photograph viewing device having an eye slit, amirror serving as a backing for the photograph, and mirrors disposed tobend the optical axis and direct separated supplies of light to thephotograph, said mirrors being separated so as to permit of the passagebetween them of rays of light to the eye slit.

15. A diffraction color-photograph viewing device having a mirrordisposed to bend the optical axis, said mirror being adjustable to varyits angle.

16. A diffraction color-photograph viewing device having an eye slit, amirror serving as a backing for the photograph, and mirrors disposed tobend the optical axis, said mir rors being separated to permit thepassage between them of rays of light to the eye slit and being alsoadjustable to vary their angle.

In testimony whereof, I have signed my 1 name to this specification, inthe presence of i two subscribing witnesses.

FREDERIC E. IVES.

WVitnesses HERBERT O. PRENTIOE, LLEWELLYN WATTs.

